Neuro-chemical sensor with inhibition of fouling on nano-electrode

ABSTRACT

A biosensor includes an array of metal nanorods formed on a substrate. An electropolymerized conductor is formed over tops of a portion of the nanorods to form a reservoir between the electropolymerized conductor and the substrate. The electropolymerized conductor includes pores that open and close responsively to electrical signals applied to the nanorods. A dispensing material is loaded in the reservoir to be dispersed in accordance with open pores.

BACKGROUND Technical Field

The present invention generally relates to biosensing devices, and moreparticularly to devices and methods to control molecular interactions ata device electrode by releasing inhibitors to prevent biofouling and/orto release growth factor to control cell growth.

Description of the Related Art

Biosensors can employ electrodes to measure properties of materials orto attract a substance being measuring or sensed. Electrodes employed onbiosensors need protection to prevent competing molecules from reactingat the electrodes. Biosensors are useful for detection of neuralactivity, such as voltage changes around active neurons or theconcentration levels of neurotransmitters. However, the lifetime ofthese biosensors in vivo can be short, due to fouling of the electrodesby accumulation of cellular materials or direct attack by the immunesystem on the biosensor.

SUMMARY

In accordance with an embodiment of the present invention, a biosensorincludes an array of metal nanorods formed on a substrate. Anelectropolymerized conductor is formed over tops of at least a portionof the nanorods to form a reservoir between the electropolymerizedconductor and the substrate. The electropolymerized conductor includespores that open and close responsively to electrical signals applied tothe nanorods. A dispensing material is loaded in the reservoir to bedispersed in accordance with open pores.

Another biosensor includes an array of metal nanorods formed on asubstrate, the array or metal nanorods being grouped into a first regionand a second region. The first region includes a first spacing betweenthe nanorods such that upon activation an electric field inconsistentwith cell activity is achieved. The second region includes a secondspacing between the nanorods such that upon activation an electric fieldconsistent with cell activity is achieved.

A method for fabricating a biosensor includes forming nanorods on ametal layer; forming a conformal layer over the nanorods; recessing theconformal layer on at least a portion of the nanorods;electropolymerizing a conductor on tops of nanorods exposed by recessingto form a reservoir between an electropolymerized conductor and themetal layer, the electropolymerized conductor including pores that openand close responsively to electrical signals applied to the nanorods;and loading a dispensing material to be dispersed in the reservoir inaccordance with open pores.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description will provide details of preferred embodimentswith reference to the following figures wherein:

FIG. 1 is a cross-sectional view showing a substrate having a metallayer, organic planarizing layer, hard mask layer and patterned resistformed thereon for forming nanorods and an encapsulation wall inaccordance with an embodiment of the present invention;

FIG. 2 is a cross-sectional view showing the substrate of FIG. 1 havingthe metal layer exposed by etching the organic planarizing layer inaccordance with the hard mask layer and the patterned resist for formingnanorods and the encapsulation wall in accordance with an embodiment ofthe present invention;

FIG. 3 is a cross-sectional view showing the substrate of FIG. 2 havingnanorods and the encapsulation wall plated and connecting to the metallayer and planarized to the hard mask layer in accordance with anembodiment of the present invention;

FIG. 4 is a cross-sectional view showing a new cross-section with threenanorods and two encapsulation walls formed on a substrate in accordancewith an embodiment of the present invention;

FIG. 5 is a cross-sectional view showing the substrate of FIG. 4 havingan atomic layer deposited coating formed on the metal layer, thenanorods and the encapsulation wall in accordance with an embodiment ofthe present invention;

FIG. 6 is a cross-sectional view showing the substrate of FIG. 5 havinganother organic planarizing layer formed and a hardmask patternedthereon in accordance with an embodiment of the present invention;

FIG. 7 is a cross-sectional view showing the substrate of FIG. 6 havingthe organic planarizing layer recessed to expose coated nanorods and theencapsulation wall in accordance with the patterned hardmask inaccordance with an embodiment of the present invention;

FIG. 8 is a cross-sectional view showing the substrate of FIG. 7 havingthe coating removed from the nanorods and the encapsulation wall thatwas exposed by the recess and having the patterned hardmask removed inaccordance with an embodiment of the present invention;

FIG. 9 is a cross-sectional view showing the substrate of FIG. 8 havingthe organic planarizing layer removed in accordance with an embodimentof the present invention;

FIG. 10 is a cross-sectional view showing the substrate of FIG. 9 havingan electropolymerized conductor formed on the exposed nanorods (and theencapsulation wall) in accordance with an embodiment of the presentinvention;

FIG. 11 is a cross-sectional view showing the substrate of FIG. 10having pores of the electropolymerized conductor opened to load adispensing material in to a reservoir in accordance with an embodimentof the present invention;

FIG. 12 is a cross-sectional view showing the substrate of FIG. 11 beingdeployed in vivo with the dispensing material loaded and cellsinteracting with the device in accordance with an embodiment of thepresent invention;

FIG. 13 is a cross-sectional view showing the substrate of FIG. 12having the dispensing material deployed through open pores in theelectropolymerized conductor in accordance with an embodiment of thepresent invention;

FIG. 14 is a cross-sectional view showing the substrate of FIG. 13 withcells reduced or eliminated from the device in accordance with anembodiment of the present invention;

FIG. 15 is a cross-sectional view showing a substrate having nanorodsspaced to produce different electric field intensities in differentregions when activated in accordance with an embodiment of the presentinvention;

FIG. 16 is a cross-sectional view showing the substrate of FIG. 15having different regions providing different functions in accordancewith an embodiment of the present invention;

FIG. 17 is a plan schematic view showing a biosensor device havingnanorods and circuits integrated on a substrate in accordance with anembodiment of the present invention; and

FIG. 18 is a block/flow diagram showing methods for fabricatingbiosensors in accordance with embodiments of the present invention.

DETAILED DESCRIPTION

In accordance with embodiments of the present invention, biosensors areemployed for measuring the presence of one or more materials in thevicinity or in contact with the biosensors. In useful embodiments, asubstrate having electronics or connections to electronics can includeone or more nanorods. The nanorods can include inert metals, such as Ptor the like. The nanorods are vertically disposed and have a diameter ortransverse width of between about 20 nm to about 3 microns, preferablybetween about 100 nm to about 500 nm, although other useful sizes arecontemplated. The nanorods can be arranged in an array or otherconfiguration on the substrate to promote collection of materials orenhance the presence of materials.

In one embodiment, the biosensors employ electrodes for detection ofneural activity, such as voltage changes around active neurons orconcentration levels of neurotransmitters. These biosensors can includeinhibition mechanisms to reduce or eliminate biofouling of theelectrodes by accumulation of cellular materials or direct attack by theimmune system on the biosensor. The electrodes are formed as nanorodsthat include the inhibition mechanism to remove or kill cells thatinterfere with sensing activities. The inhibition mechanism is employedusing the electrodes to prevent competing molecules from reacting at theelectrode.

In particularly useful embodiments, the inhibiting mechanism can inhibitor remove cellular growth from portions of a sensor or neuro sensor byapplying appropriate chemicals or growth inhibitors in specific regionsof the sensor. An implantable nano-device can address these problems bycreating structures of electrically functional nano-pillar electrodesacross a portion of a device substrate. In one embodiment, structuresfor nano-reservoirs of growth inhibitors can be provided withelectrically controlled release in adjacent portions of the devicesubstrate. The nano-device can be implanted into a desired region ofneural tissue and an appropriate timed release of the growth inhibitorsinto the growth regions from the reservoirs on the nano-device can beactivated. In other embodiments, the inhibition mechanisms can inhibitor remove cellular growth from portions of the neurosensor by applyingvoltage or electrical current in specific regions of the sensor.Combinations of these and other inhibition mechanisms can be employedtogether.

In other useful embodiments, a cell growth promoting mechanism can beemployed to stimulate cellular growth from portions of a sensor orneurosensor by applying appropriate chemicals or growth promoters inspecific regions of the sensor.

It is to be understood that aspects of the present invention will bedescribed in terms of a given illustrative architecture; however, otherarchitectures, structures, substrate materials and process features andsteps can be varied within the scope of aspects of the presentinvention.

It will also be understood that when an element such as a layer, regionor substrate is referred to as being “on” or “over” another element, itcan be directly on the other element or intervening elements can also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “connected” or “coupled” to another element, it canbe directly connected or coupled to the other element or interveningelements can be present. In contrast, when an element is referred to asbeing “directly connected” or “directly coupled” to another element,there are no intervening elements present.

The present embodiments can include a design for an integrated circuitchip, which can be created in a graphical computer programming language,and stored in a computer storage medium (such as a disk, tape, physicalhard drive, or virtual hard drive such as in a storage access network).If the designer does not fabricate chips or the photolithographic masksused to fabricate chips, the designer can transmit the resulting designby physical means (e.g., by providing a copy of the storage mediumstoring the design) or electronically (e.g., through the Internet) tosuch entities, directly or indirectly. The stored design is thenconverted into the appropriate format (e.g., GDSII) for the fabricationof photolithographic masks, which typically include multiple copies ofthe chip design in question that are to be formed on a wafer. Thephotolithographic masks are utilized to define areas of the wafer(and/or the layers thereon) to be etched or otherwise processed.

Methods as described herein can be used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case, the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case, the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product.

It should also be understood that material compounds will be describedin terms of listed elements, e.g., SiGe. These compounds includedifferent proportions of the elements within the compound, e.g., SiGeincludes Si_(x)Ge_(1−x) where x is less than or equal to 1, etc. Inaddition, other elements can be included in the compound and stillfunction in accordance with the present principles. The compounds withadditional elements will be referred to herein as alloys.

Reference in the specification to “one embodiment” or “an embodiment”,as well as other variations thereof, means that a particular feature,structure, characteristic, and so forth described in connection with theembodiment is included in at least one embodiment. Thus, the appearancesof the phrase “in one embodiment” or “in an embodiment”, as well anyother variations, appearing in various places throughout thespecification are not necessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of”, for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This can be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes” and/or “including,” when usedherein, specify the presence of stated features, integers, steps,operations, elements and/or components, but do not preclude the presenceor addition of one or more other features, integers, steps, operations,elements, components and/or groups thereof.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper,” and the like, can be used herein for ease of description todescribe one element's or feature's relationship to another element(s)or feature(s) as illustrated in the FIGs. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the FIGs. For example, if the device in theFIGs. is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the term “below” can encompass both an orientation ofabove and below. The device can be otherwise oriented (rotated 90degrees or at other orientations), and the spatially relativedescriptors used herein can be interpreted accordingly. In addition, itwill also be understood that when a layer is referred to as being“between” two layers, it can be the only layer between the two layers,or one or more intervening layers can also be present.

It will be understood that, although the terms first, second, etc. canbe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another element. Thus, a first element discussed belowcould be termed a second element without departing from the scope of thepresent concept.

Referring now to the drawings in which like numerals represent the sameor similar elements and initially to FIG. 1, a partially fabricatedbiosensor device 10 is shown in accordance with one embodiment. Thedevice 10 includes a substrate 12 having one or more layers formedthereon. The substrate 12 can include any suitable substrate structure,e.g., a bulk semiconductor, a semiconductor-on-insulator (SOI)substrate, etc. In one example, the substrate 12 can include asilicon-containing material. Illustrative examples of Si-containingmaterials suitable for the substrate 12 can include, but are not limitedto, Si, SiGe, SiGeC, SiC and multi-layers thereof. Although silicon isthe predominantly used semiconductor material in wafer fabrication,alternative semiconductor materials can be employed as additionallayers, such as, but not limited to, germanium, gallium arsenide,gallium nitride, silicon germanium, cadmium telluride, zinc selenide,etc.

Since the present embodiments provide a device that can work remotely,the device 10 can include a substrate having powered circuitry forcontrolling the functions of the device. In this way, the substrate 12can include control circuitry fabricated using known semiconductorprocessing techniques. Components can include transistors, metal lines,capacitors, logic gates or any other electronic components that permitthe control of the nanorods and other structures to be formed insubsequent steps. In one useful embodiment, bipolar junction transistors(BJT) can be employed in the circuitry formed in the substrate 12. BJTdevices can be employed to generate sub-nanosecond pulsing, as will bedescribed.

A metal layer 14 is deposited on the substrate 12 and can be employedwith other components formed in the substrate 12 (e.g., as a metallayer). The metal layer 14 can include a conductive but relatively inertmetal, such as, e.g., Pt, Au, Ag, Cu, Jr, Ru, Rh, Re, Os, Pd, and theiroxides (e.g., IrO₂, RuOx, etc.), although other metals, metal oxides andtheir alloys can be employed. The metal layer 14 can be formed bydeposition using a sputtering process, chemical vapor deposition (CVD)process, atomic layer deposition (ALD), a plating process or any othersuitable deposition process.

In one embodiment, an organic planarizing layer (OPL) 16 is formed onthe metal layer 14. The OPL 16 can be formed by a spin-on process orother deposition process. Other dielectric layers can also be employed.

An etch stop layer or hard mask 18 can be deposited over the OPL 16. Inone embodiment the etch stop layer 18 can include a metal, such as,e.g., Ti, Ta, etc. or a metallic compound such as, e.g., TiN, TaN, SiARC(a silicon containing organic ARC layer), TiARC (a titanium ARC), etc. Aresist layer 20 is formed on the etch stop layer or hard mask 18. Theresist layer 20 can be spun on. The resist layer 20 is patterned to formopenings 22 that will be employed to form nanorods and other openings 23to form an encapsulation wall as will be described.

Referring to FIG. 2, an etch process is performed to open up the etchstop layer 18. In one embodiment, a reactive ion etch (RIE) process canbe performed to expose the OPL 16 through the openings 22 and 23 (FIG.1). Then, a RIE is performed to etch through the OPL 16 to expose themetal layer 14 and form trenches 24 and 25 in accordance with the resist20 and/or the etch stop layer or hard mask 18. The trenches 24 providelocations for the formation of nanorods and an encapsulation wall. Theetch of OPL 16 should be minimized to maintain small critical dimensions(CDs) for the hole or trench 24 to be plated.

Referring to FIG. 3, a metal deposition process is performed and caninclude a plating process, CVD, sputtering or the like. The metal of thedeposition process preferably includes a same metal as employed in metallayer 14. In one particularly useful embodiment, the metal of layer 14and the metal used in nanorods 26 and an encapsulation wall 27 caninclude, e.g., Pt, Au, Ag, Cu, Jr, Ru, Rh, Re, Os, Pd, and/or theiroxides (e.g., IrO₂, RuOx, etc.), although other metals, metal oxides andtheir alloys can be employed. The nanorods 26 and the encapsulation wall27 can be annealed with the OPL 16 present or with the OPL 16 removed.If the hard mask 18 includes, e.g., Ti or TiN, the hard mask 18 can beremoved with hydrogen peroxide aqueous solution, or if it is Ti oxide orTiARC, it can be removed with diluted HF, as wet etching is simpler andeasier to control than planarization processes such as, e.g., a chemicalmechanical polish (CMP). However, a planarization process, such as,e.g., CMP, can be employed if other hard mask materials are employed.The hard mask 18 is removed down to the OPL 16. Then, the OPL 16 can beremoved by a plasma strip, e.g., oxygen plasma, forming gas plasma, witha mild wet clean to remove residues.

The encapsulation wall 27 forms a closed shape formed from metal linesconfigured to permit the formation of a reservoir. The encapsulationwall 27 can have a thickness on the same order and the nanorods 26,although any suitable thickness can be employed. In one embodiment, thewalls 27 form an open-topped polygonal structure (e.g., similar to anabove-ground pool).

Referring to FIG. 4, after the removal of the OPL 16 and the anneal ofthe nanorods 26 and encapsulation wall 27, the nanorods 26 and theencapsulation wall 27 are ready for continued processing. The nanorods26 can be arranged in any configuration suitable for creating abiosensor, e.g., an array with uniform or non-uniform spacings, etc. forchemical sensors, neurological implants or other applications.

Referring to FIG. 5, a coating 28 is formed over the nanorods 26,encapsulation wall 27 and metal layer 14. The coating 28 is formed usingALD, which can be processed to prepare a protective membrane on theelectrodes. The membrane can include a SiO₂ film although othermaterials including organic dielectrics can be employed. In oneembodiment, the coating can be formed by mixing ALD with aluminum,silicon or other materials, which can be formed in multiple layers. Eachcycle of the ALD process can deposit a layer with an oxidation processthereafter to form a respective oxide (e.g., SiO₂ or A₁₂O₃). In usefulexamples, the ALD reagent for forming Al can include AlMe₃ while thereagent for forming the SiO₂ can include (Me₂N)₃SiH (where Me is amethyl group). The ALD process can include a plurality of cycles todeposit a plurality of layers. The plurality of layers can include alarge number (e.g., two to several hundred). The plurality of layersform the coating 28, which can have a total thickness of between about 2nm to about 50 nm. While other dimensions are contemplated, the coating28 preferably includes a nanoscale thickness.

Referring to FIG. 6, another OPL 30 is formed over the coating 28. TheOPL 30 can be spun-on although other formation processes can beemployed. Another hardmask 32 is formed on the OPL 30. The hardmask 32can include a metal, such as, e.g., Ti, Ta, etc. or a metallic compoundsuch as, e.g., TiN, TaN, etc. A resist (not shown) can be employed in alithographic patterning process to pattern the etch mask 32 and protecta portion of the etch mask 32 during an etch. The etch, e.g., RIE,removes the hardmask 32 from a region 34 to open the region 34 for agrowth factor reservoir to be formed.

Referring to FIG. 7, the OPL 30 is recessed in the region 34 to exposetops 36 of the coating 28 over the nanorods 26 in the region 34. Therecess process can include a RIE selective to the coating 28 and thehard mask 32.

Referring to FIG. 8, a wet etch process can be performed to wet etchcoating 28 from the nanorods 26 and encapsulation wall 27 in the region34. The wet can include, e.g., a diluted HF etch (DHF). Another wet etchcan be performed to remove the hard mask 32 (FIG. 7) selectivelyrelative to the nanorods 26 and the OPL 30. For example, if the hardmask 32 includes Ti, a wet etch with hydrogen peroxide (H₂O₂) can beemployed to remove the hardmask.

Referring to FIG. 9, the OPL 30 is stripped to expose the coating 28 onthe nanorods 26 and the encapsulation wall 27. The OPL 30 can bestripped using a plasma etch, such as, e.g., an O₂ plasma etch orN_(2/)H₂ plasma etch. The nanorods 26 which had coating 28 removed by,e.g., a wet etch previously, are exposed within the region 34.

Referring to FIG. 10, an electropolymerization process is performed togrow a conductive porous polymer 40 on the exposed portions of thenanorods 26 and encapsulation wall 27 in the region 34. In oneembodiment, the porous polymer 40 forms an electrically responsivenanoporous membrane based on polypyrrole doped with adodecylbenzenesulfonate anion (PPy/DBS) that is electropolymerized onthe nanorods 26.

Electropolymerization is the process by which a polymer is formed usingelectrical current. The electrical current can be provided through theexposed nanorods 26 in the presence of a polymer (e.g., polypyrrole insolution). Doping can occur in-situ or after formation with theabsorption of an anion or other charged molecule. The porous polymer 40includes a regular pore size. The porous polymer 40 is configured toprovide a large volume change depending on its electrochemical state,and the pore size can be actuated electrically. The porous polymer 40 isformed in its oxidation state. The porous polymer 40 includes athickness where pores formed therein include sufficient length to passthrough the entire porous polymer layer.

The coating 28 is removed from remaining portions of the nanorods 26 andencapsulation wall 27 by a wet etch. The wet etch can include a dilutedHF etch, although other etchants can be employed. Once formed, theporous polymer 40 can have its pores opened and closed in accordancewith an electrical potential applied to the polymer 40 by nanorods 26.

Referring to FIG. 11, a growth inhibitor (or growth promoter) reservoir46 is formed using the encapsulation wall 27 between the polymer 40 andthe metal layer 14. The polymer 40 can be electrically actuated to openpores 42 through the polymer 40, which switches to the polymermaterial's reduction state (as opposed to its oxidation state). Thestate changes can be made by a potential difference of between about 0.9to about 1.2 volts applied to the nanorods 26. When the pores 42 areopened, a growth inhibiter 44 can be collected within the reservoir 46.The growth inhibitor 44 can include any useful chemical or reagent,e.g., chemotherapy drugs (e.g., cytotoxic agents, alkylating agents,anthracyclines, cytoskeletal disruptors, epothilones, histonedeacetylase inhibitors, peptide antibiotics, retinoids, etc.), hormonespecies (e.g., somatostatin, etc.), other materials, or combinations. Inalternate embodiments, a growth stimulator or promoter (44) can beloaded. The growth stimulator 44 can include any useful chemical orreagent, e.g., hormone species (e.g., steroids, etc.), metabolicstimulants, other materials, or combinations. Once growth inhibitor (orstimulator) 44 is loaded, the pores 42 of polymer 40 are closed bychanging the voltage on the nanorods 26 (and/or the encapsulation walls27).

Referring to FIG. 12, a device 50 can be placed in vivo by surgery orinjection. As cells 47 interact with the surface of the device 50, thecells 47 can begin to grow or otherwise interfere with the operation ofthe device 50. For example, the device 50 can be placed in vivo to senseor measure concentrations of materials within the body. When cells 47begin to affect function of the device 50, the growth inhibitorreservoir 46, which is loaded with growth inhibitor 44, can beselectively exposed to release growth inhibiter material. Electrodes(nanorods 26) in region 34 are activated to open from the closedposition depicted in FIG. 12.

Referring to FIGS. 13 and 14, electrodes (nanorods 26) in region 34 areactivated to open the pores 42 or the polymer 40 to an open position.This permits growth inhibitor 48 to be released through the pores 42.The growth inhibitor 48 includes a dosage that will provide biofoulinginhibition without significant damage to other surrounding tissues. Thegrowth inhibitor 48 interferes with growth of the cell or cells 47reducing the size of the cell 47 and/or its influence on the device 50as depicted in FIG. 14.

The opening of the pores 42 can be performed in a pulsatile (oron-demand) manner so that the release of growth inhibitor 48 can becarefully controlled. A switching time of a few seconds or less can beemployed to provide local and on-demand delivery of the growth inhibitor48. The pores 42 can be reclosed until activated at a later time tofurther inhibit biofouling. In alternate embodiments, a growthstimulator or promoter (44) can be deployed instead of the growthinhibitor to stimulate cell growth or to treat a wound or other tissue.

Referring to FIG. 15, in other embodiments, inhibitor mechanisms canemploy the nanorods 26 to inhibit or remove cellular growth fromportions of a device 58 (e.g., a neurosensor) by applying appropriatevoltage or electrical current in specific regions of the device 58. Thedevice can include one or more regions 54, 56.

The device 58, e.g., a biosensors, can incorporate a combination ofactive sensor regions 56 and also regions 54 of cell growth inhibition.The nanorods 26 in region 54 can, for example, have a narrow spacing 60(e.g., between about 20 nm-1000 nm), such that a common voltage appliedto all nanorods 26 results in a higher electric field intensity betweenthe narrower spacings 60. The electric field intensity can be controlledby adjusting voltage (e.g., between about 0.5 volts to about 100 volts(or higher)) and current conditions using circuit components or controlsintegrated into the device 58. In useful embodiments, the nanorods 26 inregion 54 can be subjected to nanosecond (e.g., 0.1 ns to about 500 ns)pulsed electric fields (nsPEF) which can induce apoptosis in cells.

It should be understood that electric field intensity can be adjusted ina plurality of ways. For example, the size, shape and density of thenanorods 26 can be controlled. In other embodiments, pulse shapes andpulse frequencies can be adjusted and controlled for pulsations ofvoltage or current to the nanorods. Other electric field intensitycontrols are also contemplated, e.g., nanorod coatings, such as, e.g., aporous protective coating, biofouling coating, electrical insulatinglayers, etc.

The biosensor regions 56 can have an increased spacing 62 to reduceelectric field intensity to permit cell growth for measurement orsensing operations. In some embodiments, the biosensor regions 56 can becontrolled to change from an active sensing region to a growthinhibition region using the voltage or current conditions as controlledby the circuit components or controls integrated into the device 58. Inthis way, regions or the entire sensor surface can be periodicallycleansed of cellular material by appropriate control of voltage andcurrent conditions.

The nanorods 26 can be formed at different pitches and configurationsduring the patterning process as depicted in FIG. 1. The nanorods 26 canbe configured for specific tasks including protecting the device 58 frombiofouling, to sense the presence of bio or chemical material and/or totreat specific diseases or enable sensor functionality.

Referring to FIG. 16, in one embodiment, region 54 prevents or inhibitscellular growth while region 56 stimulates cell growth. For example,region 56 can permit electrical stimulation of neuro-stem cells 64, inplace on the device 58. Cell 64 can be bound to nanorod electrodes 26 inregion 56, which includes an electrical pulsation that stimulates cellgrowth. The cells 64 can be employed in a treatment program, e.g., invivo. Therefore, depending on the application, growth inhibition orgrowth stimulation can be provided in accordance with the presentembodiments depending on the electrical settings and environmentalconditions created. An example of environmental conditions created forgrowth inhibition can include the introduction of biofouling reducingchemical or materials. An example of environmental conditions createdfor growth stimulation can include incorporating growth factors into thechemical storage region, rather than growth inhibitors, e.g., for a stemcell application.

Referring to FIG. 17, a device 70 for inhibiting biofouling or promotinggrowth is illustratively shown in accordance with one embodiment. Thedevice 70 includes an array 72 of electrodes 80. The array 72 includesuniform spacings between electrodes 40; however, non-uniform spacingscan be employed. An illustrative encapsulation wall 27 is shown to forma reservoir 46. A circuit 74 can include an array of transistors and/orother circuit components (e.g., integrated into the substrate 12)configured to activate or selectively activate electrodes. The circuit74 can be integrated into the substrate 12 using semiconductorprocessing techniques. The circuit 74 can include a high voltage powersource, e.g., if the device 70 is implantable in the body.Alternatively, the circuit 74 can connect to a separate external powersource.

The circuit 74 can be controlled using a controller circuit 76 thatgenerates signals to control which electrodes 80 are activated. The highvoltage (e.g., 0.5 to 100 volts) can be programmed to activate theelectrodes 80 using a patterned metal layer 14 to connect to theelectrodes 80 in localized areas to prevent cell growth over specificregions of the array 72 or the whole array 72. The activation of theelectrodes can prevent cell growth or selectively kill cells in theseregions or parts of cells in the region. The activation of theelectrodes can also promote cell growth or selectively grow cells inthese regions or parts of cells in the region.

Device 70 can also include a biosensor that employs biologicalrecognition properties for selective detection of various analytes orbiomolecules. The biosensor 70 can generate a signal or signals thatquantitatively relate to a concentration of the analyte on or near theelectrodes 80. To achieve a quantitative signal, a recognition moleculeor combination of molecules can be immobilized at the electrodes 80,which convert the biological recognition event into a quantitativeresponse.

In some embodiments, the nanorod electrodes 80 can produce electricalfields for inhibiting biofouling, stimulating cell growth, releasingdrugs or growth inhibitors or combinations of these tasks. In anotherembodiment, a radiation source 84, such as, e.g., a laser, nuclearradiation source or the like can direct radiation 86 to selectively killcells in specific regions of the device 70. The device 70 can oscillatebetween measuring cycles and cycles to inhibit biofouling using, e.g.,high voltage pulses or the like.

Device 70 can include regions with different spacings between nanorods80 (e.g., region 88). Device 70 can include different biofoulinginhibiting mechanisms and can include electrical based systems usingspacings and electrical pulses to cause cell reduction or death and/orpromoter/inhibiter dispensing mechanisms or combinations of these orother mechanisms. The device 70 can be made disposable after use. Thesubstrate 12 and other components can be coated or shielded to preventcontamination to the host from materials of the device 70.

Referring to FIG. 18, methods for fabricating biosensors areillustratively shown and described. In some alternative implementations,the functions noted in the blocks may occur out of the order noted inthe figures. For example, two blocks shown in succession may, in fact,be executed substantially concurrently, or the blocks may sometimes beexecuted in the reverse order, depending upon the functionalityinvolved. It will also be noted that each block of the block diagramsand/or flowchart illustration, and combinations of blocks in the blockdiagrams and/or flowchart illustration, can be implemented by specialpurpose hardware-based systems that perform the specified functions oracts or carry out combinations of special purpose hardware and computerinstructions.

In block 102, nanorods are formed on a metal layer. The metal layer onwhich the nanorods are formed can be patterned to provide electricalconnections to the nanorods or groups of nanorods.

In block 104, the nanorods can be connected to a circuit to provideselective activation of the nanorods as electrodes. The circuit caninclude an integrated circuit formed within the same substrate as thenanorods are formed on. Alternately, the circuit or chip can connect orbe integrated with the substrate with the nanorods. Metal paths can beformed by patterning the metal layer on which the nanorods are formed.

In block 106, a conformal layer is formed over the nanorods by, e.g.,atomic layer deposition by depositing layers of aluminum or silicon andoxidizing. It should be understood that while Si and Al are preferredmaterials, other materials or combinations can be employed to form acoating or membrane.

In block 108, the conformal layer is recessed in at least one region(e.g., over a portion of the nanorods). This can include patterning ahardmask over a portion of the device and etching a protective layer,e.g., OPL, until tops of the coated nanorods are exposed. The exposetops are etched to remove the coating and expose the nanorods. The hardmask and OPL or other protective material can then be removed.

In block 110, a polymer conductor is electropolymerized on tops ofnanorods exposed by recessing to form a reservoir between theelectropolymerized conductor and the metal layer. The electropolymerizedconductor includes pores that open and close responsively to electricalsignals applied to the nanorods. The electropolymerized conductor caninclude polypyrrole, which can be doped with anions to be formed in itsoxidation state.

In block 112, a dispensing material to be dispersed is loaded in thereservoir in accordance with open pores. The pores are held open byapplying an electric field to the electropolymerized conductor (e.g.,using nanorods). The dispensing material is applied to the device andsettles through the open pores.

In block 114, the pores are closed for in vivo delivery and operationusing a voltage on the nanorods. In block 116, in vivo or otherwise, thepores are opened to dispense the dispensing material in accordance withelectrical signals. The electrical signals can be pulsed to providebetter control of an amount of dispensing material released. Thedispensing material can include a cell growth inhibitor, cell growthpromoter, drug, or other materials. In one embodiment, the dispensingmaterial can include a growth factor, such as, e.g., a neurotrophicgrowth factor, to stimulate the growth of stem cells, or other growthfactors, such as, e.g., hormones (e.g., steroids), cytokines, or otherproteins and stimulants.

The nanorods can be grouped into a first region and a second regionwhere the first region includes the electropolymerized conductor anddispenses material using electric fields on narrowly spaced nanorods orother biofouling inhibition mechanism. A second region can include asensing region, a cell growth region, etc. The first region can inhibitbiofouling in at least first region or in both the first and secondregion. This can be performed intermittently or as needed. Thedispensing material can be dispersed two or more times by opening andclosing the pores when needed.

Having described preferred embodiments for a neuro-chemical sensors withinhibition of fouling on nano-electrodes (which are intended to beillustrative and not limiting), it is noted that modifications andvariations can be made by persons skilled in the art in light of theabove teachings. It is therefore to be understood that changes may bemade in the particular embodiments disclosed which are within the scopeof the invention as outlined by the appended claims. Having thusdescribed aspects of the invention, with the details and particularityrequired by the patent laws, what is claimed and desired protected byLetters Patent is set forth in the appended claims.

What is claimed is:
 1. A method for fabricating a biosensor, comprising:forming nanorods on a metal layer; forming a conformal layer over thenanorods; recessing the conformal layer on at least a portion of thenanorods; electropolymerizing a conductor on tops of nanorods exposed byrecessing to form a reservoir between an electropolymerized conductorand the metal layer, the electropolymerized conductor including poresthat open and close responsively to electrical signals applied to thenanorods; and loading a dispensing material to be dispersed in thereservoir in accordance with open pores.
 2. The method as recited inclaim 1, further comprising closing the pores for in vivo operation. 3.The method as recited in claim 2, further comprising opening the poresto dispense the dispensing material.
 4. The method as recited in claim1, wherein the electrical signals are pulsed to control an amount ofdispensing material released.
 5. The method as recited in claim 1,wherein the dispensing material includes a cell growth inhibitor or acell growth promoter.
 6. The method as recited in claim 1, wherein theelectropolymerized conductor includes polypyrrole.
 7. The method asrecited in claim 1, wherein the nanorods are grouped into a first regionand a second region where the first region includes theelectropolymerized conductor and the dispensing material, and a secondregion includes a sensing region.
 8. The method as recited in claim 1,wherein the first region inhibits biofouling in at least the firstregion.
 9. The method as recited in claim 1, wherein the first regioninhibits biofouling in the first region and the second region.
 10. Themethod as recited in claim 1, wherein the dispensing material can bedispersed two or more times.